KR20150113546A - The composition of ceramic suspension for the ceramic suspension thermal spray coating to the metal surface - Google Patents

Abstract

The present invention relates to a composition of ceramic suspension for conducting thermal spray coating of ceramic suspension on a metal surface and, more specifically, to a composition of ceramic suspension for conducting thermal spray coating of ceramic suspension on a metal surface, wherein ceramic coating is conducted on the surface of metal-composed components such as turbine engines, air foil bearings, gear chlorine gas compressing rods, heat exchanger deck and channel covers, pipes, heat exchangers, motor housings, ball valves, air blowers, sleeves and pump liners to grant abrasion resistance. According to the present invention, a high-density coating film can be manufactured by overcoming the disadvantages of a traditional thermal plasma spray method as raw materials can be supplied in the state of suspension having ceramic powder dispersed in a liquid state instead of granular powder.

Description

Technical Field [0001] The present invention relates to a ceramic suspension composition for spraying a ceramic suspension onto a metal surface,

The present invention relates to a ceramic suspension composition for spray coating a ceramic suspension on a metal surface, and more particularly to a ceramic suspension composition for coating a ceramic suspension on a metal surface, A ceramic suspension composition for spray coating a ceramic suspension on a metal surface for coating a ceramic to impart abrasion resistance to surfaces of metal parts such as heat exchangers, motor housings, ball valves, blowers, sleeves, pump liner will be.

In general, spray coating is a method of spraying a coating material of wire and powder material in a molten state on the surface of an adherend in order to improve abrasion resistance, corrosion resistance, heat resistance, electrical conductivity and insulation properties of a mechanical part Coating. Flame, plasma, arc and the like are used as the heat source of the spray coating. As the spray coating material, metal, ceramics, composite materials, etc. can be used variously according to required performance.

The spray coating can form a coating layer with a thickness of up to several tens of millimeters, and it is also possible to coat a coating material having a large area or complicated shape. In addition, spray coating can be applied to various structures such as marine structures, shipbuilding materials, power plants, boiler facilities, transmission towers, and bridges. The important factors of spray coating are the temperature of the heat source, the injection speed of molten particles, the injection distance of the sprayer and the coating material, and the moving speed of the sprayer.

Typically, the spray coating is an arc plasma spraying method in which a material to be coated is supplied in a wire form to form a coating film at a high speed on a large-sized article, and a thermal plasma spraying method in which the powder is supplied in a granule shape.

In the case of the arc plasma spraying, since the coating material must be manufactured in a line shape, it is limited to the coating of the metal material and can not be applied to the manufacture of the ceramic coating film having excellent erosion resistance.

In the case of thermal plasma spraying, a ceramic material can be used because granular powder is used. However, since granules having a size of about 30 to 200 micrometers are used, Large pores are present to cause a problem that the density of the coating film is low, the adhesion with the base material is decreased, and a plurality of defects are formed in which a layered microstructure is formed, thereby deteriorating the characteristics of the coating film.

That is, in Korean Patent Laid-Open No. 10-2006-0021625, four components of "Cr ₂ O ₃ , NiCr, Ag, and BaF ₂ / CaF ₂ are combined to form one particle, Characterized in that it has a high-temperature abrasion resistance and a high frictional resistance, characterized by being 10-50% of Cr ₂ O ₃ having a size of 300 nm or less, 50-70% of NiCr, 5-15% of Ag and 5-15% of BaF ₂ / CaF ₂ Quot; coating powder for use "was presented,

Korean Patent Laid-Open No. 10-2008-0039317 discloses that "the average particle size of the primary particles constituting the granulated and sintered particles is 2 to 10 μm and the granulated and sintered particles have an average particle size of 7 to 50 MPa &Quot; < / RTI > a granulated powder comprising granulated and sintered particles comprising an oxide of any one of the rare earth elements of any one of < RTI ID = 0.0 > 60-70. ≪ / RTI >

However, the use of granular ceramics lowers the density of the coating film due to the presence of large pores in the coating film, deteriorates adherence to the base material, and forms a layered microstructure, thereby deteriorating the physical properties of the coating film.

Therefore, there is an urgent need to develop a ceramic coating having improved corrosion resistance and abrasion resistance by increasing the adhesion with a base material by preparing a high-density coating film.

Korean Patent Publication No. 10-2006-0021625 Korean Patent Publication No. 10-2008-0039317

In order to solve the above problems, the present invention provides a ceramic suspension composition capable of forming a nanometer-scale high-density coating film excellent in adhesion, corrosion resistance and abrasion resistance by thermal plasma spraying.

According to the present invention, particles comprising at least one selected from the group consisting of Y ₂ O ₃ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ and YSZ as ceramic particles; And water used as a solution, wherein the ceramic particles have a particle size of 0.4 to 8 μm (micrometer), the pH value of the ceramic suspension composition composed of the ceramic particles and water is 7.5 to 8, and the ceramic suspension The composition may further comprise a dispersant as an additive, and the dispersant may be any one selected from PAA, PEI, or PBTCA. A ceramic suspension composition for spray coating a ceramic suspension on a metal surface may be provided .

In the ceramic suspension composition, a mixed composition of Y ₂ O ₃ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ and YSZ may be contained as the ceramic particles.

The suspension solution may be optimized when the pH value of the ceramic suspension composition (in the absence of an additive) composed of the ceramic particles and water is 7.5 to 8.

The content of ceramic particles in the ceramic suspension composition may be from 15 vol.% To 25 vol.%, Based on the total ceramic suspension composition.

According to the present invention, since the raw material can be supplied in a suspension state in which the ceramic powder is dispersed in the liquid state instead of the granular powder, the high density coating film can be manufactured by overcoming the disadvantage of the conventional thermal plasma spraying method. Also, by using the ceramic suspension composition according to the present invention, it is possible to form a coating layer having nanostructured microstructure, so that a coating film having excellent properties can be produced. That is, the ceramic coating film prepared using the ceramic suspension composition according to the present invention is excellent in corrosion resistance and abrasion resistance because it forms a nanometer-scale high-density coating film.

1 is a view of an embodiment showing a thermal plasma spray coating.
2A to 2D are diagrams showing the microstructure of the particle size.
3 is a view showing data obtained by analyzing particle size.
4 is a graph showing zeta potential data for a ceramic mixed powder.
FIG. 5 is a view showing an embodiment showing a viscosity change according to a powder content. FIG.
Figure 6 is a plot of measured viscosity values for suspension solutions prepared according to the concentration of each of the various dispersants.
Fig. 7 is a graph showing the change in viscosity with the inclusion of the PEI dispersant. Fig.
8A to 8C are photographs of a cross-sectional layer coated on a metal surface 50 times by SEM.
9A to 9C are photographs of a zirconia cross-section layer coated with a metal surface 100 times by SEM.

Hereinafter, a ceramic suspension composition for coating a ceramic suspension on a metal surface according to an embodiment of the present invention will be described in detail.

The detailed description of common techniques necessary for explaining the present invention can be omitted.

For the spray coating process of the present invention, an arc plasma spraying apparatus for supplying a material to be coated in a wire form and a granule are supplied in the form of a granular powder, Thermal Plasma Spray equipment.

In the case of arc plasma spraying, since the coating material is to be manufactured in a line shape, it is limited to the coating of a metal material and can not be applied to the production of a ceramic coating film having excellent erosion resistance. In the case of thermal plasma spraying, However, since granules having a size of about 30 to 200 mu m are used, large pores are present in the coating film due to problems such as non-melting of the granules, the density of the coating film is low, the adhesion with the base material is decreased, And a plurality of defects are formed in the microstructure of the substrate, thereby deteriorating the characteristics of the coating film.

The suspension plasma spray coating using the ceramic suspension composition according to the present invention has a structure similar to that of the thermal plasma spray coating, but it can overcome the disadvantage of the thermal plasma spraying method. That is, instead of the granular powder, it is possible to supply the raw material in a suspension state in which the ceramic powder is dispersed in a liquid state, so that a high-density coating film can be manufactured and nanostructure microstructure can be formed, .

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a view of an embodiment showing equipment for thermal plasma spray coating.

The composition of the ceramic powder used in the present invention may be selected from the group consisting of Y ₂ O ₃ (yttria), TiO ₂ (titania), ZrO ₂ (zirconia), Al ₂ O ₃ (alumina) and YSZ (yttria-stabilized zirconia ), Etc., and the ratios of the materials used are wt% Y ₂ O ₃ : 10 to 50%, TiO ₂ : 50 to 70%, ZrO ₂ : 5 to 15%, Al ₂ O ₃ : , And YSZ: 10 to 50%. On the other hand, YSZ can be used as a single ceramic material, and Y ₂ O ₃ , TiO ₂ , ZrO ₂ and Al ₂ O _{3 can} also be used as a single ceramic material.

TiO ₂ reduces the coefficient of thermal expansion with respect to the base material and serves as a metal binder in the coating, and TiO ₂ is preferably contained in an amount of 50-70 wt%. If the content is less than 50wt%, the coating layer and the mothayeo bear properly on the operating temperature and load conditions after the occurrence and coating peeling of mothayeo insufficient relaxation of the thermal stress between the base coat layer bearing an oxide or peeling occurs, and greater than 70wt% TiO ₂ It may be difficult to expect the content of the lubricating properties and dispersion of other components after coating.

Y ₂ O ₃ , which is a light material, is a material having an acid strengthening function in the coating and a lubricating property at about 800 ° C. It is preferably contained in an amount of 10-50 wt.%. This is because a large amount of Y ₂ O ₃ may deteriorate the friction characteristics in a low temperature region.

The ZrO ₂ and Al ₂ O ₃ components are excellent lubricating materials, but they are limited to 5-15 wt% in order to lubricate them with a minimum amount in view of cost.

In addition, the ceramic composition powder according to another embodiment of the present invention includes Cr ₂ O ₃ (chromium oxide), NiCr, Ag and BaF ₂ / CaF ₂ (barium fluoride / calcium fluoride) May be 10 to 50% of Cr ₂ O ₃ , 50 to 70% of NiCr, 5 to 15% of Ag and 5 to 15% of BaF ₂ / CaF _{2 in terms} of wt%.

In addition, a ceramic suspension composition for spraying a ceramic suspension on a metal surface of the present invention will be described as an example.

- Suspension dispersion preparation -

Hereinafter, a basic composition for preparing a suspension dispersion and a method for producing particles will be described.

First, to prepare a suspension dispersion, water is used as a solvent and the content of the powder is made 1 to 20 volume percent.

In this case, the ceramic material of Example 1 may be prepared by using YSZ alone or by using a ceramic composition (10 to 50% Y ₂ O ₃ , 50 to 70% TiO ₂ , 5 to 15% ZrO ₂ , Al ₂ O ₃ : 5 to 15%, and YSZ: 10 to 50%). In some cases, Y ₂ O ₃ , TiO ₂ , ZrO ₂ and Al ₂ O ₃ can be used alone.

To prepare the initial powder, ceramic mixed powder is used and ball milling is performed to prepare solid contents, and distilled water is mixed. A dispersant or the like is added as an additive to prepare a suspension solution. At this time, conditions of ball milling are shown in Table 1.

 Ball milling conditions Raw material Ceramic mixed powder Milling method Ball milling Milling time 3hr RPM 120

Powder analysis was performed using a scanning electron microscope and a laser diffraction particle size analysis for the shape and size of the raw material powder. The microstructure was shown in FIGS. 2A to 2D and the particle size analysis data was shown in FIG.

As a result of analyzing the shape and the particle size analysis data of the powder used in the present invention, it was found that the powder had a very polygonal shape and was manufactured through a top down process. The particle size distribution was 0.4 to 8um And the mean value was 1.17um. In order to optimize the suspension solution in the present invention, in order to achieve agglomeration according to the pH control in the absence of the additive, a solution of each pH concentration is prepared, and the zeta potential Isoelectric point (IEP) was analyzed. The isoelectric point of the powder was confirmed to be a pH of about 7.5-8. In addition, the zeta potential data for the ceramic mixed powder is shown in Fig.

Suspension solution The viscosity was measured by adding 1-20% of the content of the powder in the state of not adding the dispersing and dispersing agent, and as a result, the viscosity was 2 to 25 mPa.s, and detailed data thereof is shown in FIG. 5 is a view of an embodiment showing the viscosity change according to the powder content.

As expected, the viscosity increased as the amount of powder increased. When the content of the powder was 15 vol% or more, it was confirmed that the viscosity increased sharply.

To investigate the effect of dispersant on suspension viscosity, three different dispersants used in YSZ were used.

1. PAA (ammonium polyacrylic acid)

2. Polyethylene imine (PEI)

3. PBTCA (2-phosphonobutane tricarboxylic acid)

Experiments were conducted using three different dispersants to stabilize the dispersion of the suspension solution. That is, in the present invention, suspensions were prepared according to the concentration of various dispersants, and FIG. 6 is a view showing measured viscosity values for the suspension solution prepared according to the concentration of each of various dispersants.

As shown in the drawing of FIG. It was confirmed that the viscosity was similar to 0.005 wt% for PAA, 0.05% for PEI, and 0.05 wt% for PBTCA.

The three types of dispersants were found to reduce the viscosity from 8 to 23 mPa for suspension solutions with 20 vol% powder content, respectively. At this time, the change range of the powder can be changed from 15vol% to 25vol%. That is, if it is lower than 15 vol%, it is difficult to sufficiently coat the particles, and when it exceeds 25 vol%, the viscosity becomes too high, so that the spray coating is not performed well.

 In the case of PEI and PBTCA dispersants, the viscosity was minimal up to 0.005 wt%, unlike PAA dispersants.

Fig. 7 is a graph showing the change in viscosity with the inclusion of the PEI dispersant. Fig. The content of the powder and the viscosity according to the PEI dispersant.

When the content of the powder is large, the dispersing agent sharply reduces the viscosity of the suspension solution. However, when the content of the powder is small, the value of the viscosity has a similar value regardless of the dispersing agent.

This phenomenon seems to be caused by the interaction between particles and particles when the content of the powder is large. Therefore, the added dispersant may have a greater effect. Suspension solution without dispersant can be precipitated quickly even when the content of the powder in the suspension solution is small, and it may be difficult to redisperse by forming a particle layer after precipitation. Suspension solutions containing dispersants, on the other hand, tend to settle very slowly and can be easily redispersed after precipitation.

Ceramic spray coating was performed on the metal surface using the ceramic current-collecting solution prepared through the above-described examples. As a result, a dense cross-sectional structure was shown as in Figs. 8A to 8C and Figs. 9A to 9C.

That is, FIGS. 8A to 8C are SEM images of a cross-sectional layer coated on a metal surface 50 times, and it is shown that the coating film has a thickness of about 25 μm and has a dense cross-sectional structure. 9A to 9C are photographs of a zirconia cross-section coated on a metal surface 100 times by SEM. It was confirmed that a coating layer was formed with a thickness of about 50 μm and a dense coating film without pores was formed.

 Therefore, by using the composition according to the present invention, it is possible to form a dense and high-density coating film, thereby enhancing the adhesion with the base material, thereby forming a ceramic coating having improved corrosion resistance and abrasion resistance.

Claims (2)

A mixed composition of Y ₂ O ₃ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ and YSZ as ceramic particles; And
1. A ceramic suspension composition comprising water used as a solution,
The particle size of the ceramic particles is 0.4 to 8 um,
The pH value of the ceramic suspension composition composed of the ceramic particles and water is 7.5 to 8,
The ceramic suspension composition further comprises a dispersant as an additive,
Wherein the dispersant is one selected from the group consisting of PAA, PEI, and PBTCA. ≪ RTI ID = 0.0 > 8. < / RTI > A ceramic suspension composition for spray coating a ceramic suspension on a metal surface.
The method according to claim 1,
Wherein the content of ceramic particles in the ceramic suspension composition is 15 vol% to 25 vol% based on the total of the ceramic suspension composition.

Images